linux-kernel - [PATCH 1/2] scftorture: Move memory allocation outside of preempt

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Message-ID: <20241104105053.2182833-1-bigeasy@linutronix.de>
Date: Mon,  4 Nov 2024 11:50:52 +0100
From: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To: "Paul E. McKenney" <paulmck@...nel.org>
Cc: Boqun Feng <boqun.feng@...il.com>,
	Vlastimil Babka <vbabka@...e.cz>,
	Marco Elver <elver@...gle.com>,
	linux-kernel@...r.kernel.org,
	kasan-dev@...glegroups.com,
	linux-mm@...ck.org,
	sfr@...b.auug.org.au,
	longman@...hat.com,
	cl@...ux.com,
	penberg@...nel.org,
	rientjes@...gle.com,
	iamjoonsoo.kim@....com,
	akpm@...ux-foundation.org,
	Tomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Subject: [PATCH 1/2] scftorture: Move memory allocation outside of preempt_disable region.

Memory allocations can not happen within regions with explicit disabled
preemption PREEMPT_RT. The problem is that the locking structures
underneath are sleeping locks.

Move the memory allocation outside of the preempt-disabled section. Keep
the GFP_ATOMIC for the allocation to behave like a "ememergncy
allocation".

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
---
 kernel/scftorture.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/kernel/scftorture.c b/kernel/scftorture.c
index 44e83a6462647..e5546fe256329 100644
--- a/kernel/scftorture.c
+++ b/kernel/scftorture.c
@@ -320,10 +320,6 @@ static void scftorture_invoke_one(struct scf_statistics *scfp, struct torture_ra
 	struct scf_check *scfcp = NULL;
 	struct scf_selector *scfsp = scf_sel_rand(trsp);
 
-	if (use_cpus_read_lock)
-		cpus_read_lock();
-	else
-		preempt_disable();
 	if (scfsp->scfs_prim == SCF_PRIM_SINGLE || scfsp->scfs_wait) {
 		scfcp = kmalloc(sizeof(*scfcp), GFP_ATOMIC);
 		if (!scfcp) {
@@ -337,6 +333,10 @@ static void scftorture_invoke_one(struct scf_statistics *scfp, struct torture_ra
 			scfcp->scfc_rpc = false;
 		}
 	}
+	if (use_cpus_read_lock)
+		cpus_read_lock();
+	else
+		preempt_disable();
 	switch (scfsp->scfs_prim) {
 	case SCF_PRIM_RESCHED:
 		if (IS_BUILTIN(CONFIG_SCF_TORTURE_TEST)) {
-- 
2.45.2